Snapshotting Worflow

Snapshotting is a technique provided by tc to capture the Topology definition along with all the sub versions of its nodes and entities. It is not to be confused with a manifest of versions. We can freeze a sandbox, snapshot it, store the snapshot in S3 or filesystem and render the snapshot of a Topology in any sandbox and profile.

Following is the structure of a snapshot:

[{
    "changed": true,
    "changelog": ["PR-1123 ..."],
    "dir": "./path/to/topology",
    "git_version": "",
    "kind": "routed",
    "namespace": "topo-1",
    "prev_version": "",
    "sandbox": "stable",
    "tc_version": "",
    "updated_at": "",
    "updated_by": "",
    "version": "0.1.1",
    "topology": Topology
}]

Note

The snapshot contains the partially rendered topology containing various sub-versions and resolved entity attributes. The version is the root entity’s version and not any entity’s version. This is by design as the root entity always gets updated last. The root entity’s version is also used as a way to potentially rollback.

1. Freeze

   tc freeze -s stable -e qa

   Freeze is a software-enforced freeze. Test! Test! Test! after freeze.

2. Snapshot

   tc snapshot -s stable -e qa --save

   This saves the snapshot of manifests, changelog and topology definitions to s3.

3. Unfreeze

   tc unfreeze -s stable -e qa

   This allows Continuous deploys to continue.

4. Promote

   To promote a snapshot, we first go back and pick the one that has been certified and tested in QA. For example:

   tc snapshot --list
   qa/stable/2025-10-02
   qa/stable/2025-10-01
   qa/stable/2025-09-30
   qa/stable/2025-09-29
   qa/stable/2025-09-18

   To deploy a snapshot (say qa/stable/2025-10-02), we do:

    tc ci-deploy --env prod --sandbox stable --snapshot qa/stable/2025-10-02

   Behind the scenes, ci-deploy triggers a pipeline using the snapshot:

   tc snapshot --show qa/stable/2025-10-02 -f pipeline --target-env dev --target-sandbox stable

Managing Snapshots

To list snapshots:

tc snapshot --list

qa/stable/2025-10-02
qa/stable/2025-10-01
qa/stable/2025-09-30
qa/stable/2025-09-29
qa/stable/2025-09-18

To view a snapshot

tc snapshot --show qa/stable/2025-10-02

To view the pipeline generated for a snapshot

tc snapshot --show qa/stable/2025-10-02 -f pipeline --target-env dev --target-sandbox stable

Snapshotter API Service

At times, we may need to run the snapshotter commands with a checkout of your code. We can run it in a microvm. Example

TC_ASSET_BUCKET=my-bucket tc create -s yoda -e dev
=> microvm-url

curl -X POST microvm-url -d '{"command": "snapshot", "env": "qa", "sandbox": "stable"}'